Rachel babysits for her sister for no pay. When she babysits for someone else she charges $8 an hour. When is Rachel’s babysitting included in GDP?

a. When she babysits for her sister and when she babysits for someone else.
b. When she babysits for her sister, but not when she babysits for someone else.
c. Neither when she babysits for her sister nor for someone else.
d. When she babysits for someone else, but not when she babysits for her sister.